I don't believe Du actually see them KISS (yet), but after rewatching the series, I noticed at the end of season 1 the following scene: Moka and Tsukune are about to kiss, but the other girls come in. They go on about how they should finish with them, then Moka jumps in and says, "No just let me KISS him!" It then goes to a black screen and five pairs of lips appear. So unless one of those lips were the bat oder Moka was sucking his blood, I would warrant that as a kiss.
